Mobile station use of round trip time measurements

ABSTRACT

Techniques are provided in which a mobile station may determine a first round-trip time (RTT) for a first measurement related communication between the transceiver and a first network device, wherein the first RTT comprises a uniform delay of time applied during the first measurement related communication by the first network device; Determine a second RTT for a second measurement related communication between the transceiver and a second network device, wherein the second RTT comprises the uniform delay of time applied during the second measurement related communication by the second network device; and determine, at least in part, a position of the mobile station with regard to at least the first and second network devices based, at least in part, on the first RTT and the second RTT.

CLAIM OF PRIORITY UNDER 35 U.S.C. 120

This application is a continuation of U.S. application Ser. No.13/752,270, filed Jan. 28, 2013, entitled “Device for Round Trip TimeMeasurements,” which is a continuation of U.S. application Ser. No.12/772,029, filed Apr. 30, 2010, entitled “Device for Round Trip TimeMeasurements,” each of which are assigned to the assignee hereof andincorporated herein by reference.

BACKGROUND

1. Background Field

Aspects of the present disclosure generally relate to wirelesscommunication systems, and more specifically, to position determinationfor mobile stations by facilitating accurate measurement of a round triptime (RTT) using a dedicated network appliance.

2. Relevant Background

Mobile communications networks are offering increasingly sophisticatedcapabilities associated with position location. New softwareapplications, such as, for example, those related to personalproductivity, collaborative communications, social networking, and dataacquisition, may use position information to provide new features andservices to consumers. Aside from the sizeable commercial potential,regulatory requirements in some jurisdictions may require a networkoperator to report the location of a mobile station when the mobilestation places a call to an emergency service, such as a 911 call in theUnited States.

Position determination has conventionally been provided using digitalcellular positioning techniques, Satellite Positioning Systems (SPS's)and the like. In conventional digital cellular networks, positionlocation capability can also be provided by various time and phasemeasurement techniques from points with a known location such as accesspoints or base stations. For example, one position determinationapproach used in CDMA networks is referred to as Advanced Forward LinkTrilateration (AFLT). Using AFLT, a mobile station may compute itsposition from phase measurements of pilot signals transmitted from aplurality of base stations.

Improvements to AFLT have resulted from the hybrid position locationtechniques, for example, where the mobile station may employ a SatellitePositioning System (SPS) receiver in addition to measurement techniquesassociated with the reception of base station signals. The SPS receiverprovides position information independent of the information derivedfrom the signals transmitted by the base stations. Position accuracy canbe improved by combining measurements derived from both SPS and AFLTsystems using conventional techniques.

However, conventional position location techniques based upon signalsprovided by SPS and cellular base stations may encounter difficultieswhen the mobile station is operating within a building and within urbanenvironments or in situations when high accuracy is desired. In suchsituations, signal reflection and refraction, multipath, and signalattenuation, and the like can significantly reduce position accuracy,and can slow the “time-to-fix” to unacceptably long time periods. Theseissues may be overcome using signals from other existing wirelessnetworks, such as, for example, Wi-Fi standards under 802.11x, to deriveposition information. Conventional position determination techniquesused in other existing wireless networks may use round trip time (RTT)measurements derived from signals used within these networks.

RTT measurements from stations (STA) to access points (APs) in shortrange radio or wireless communication networks, such as 802.11 or Wi-Finetworks, Bluetooth networks, and the like, can be used to determine thelocation of or localize a station via trilateration. As is understood bythose of skill in the art, trilateration is used to determine theintersections of three circular or four spherical areas given thecenters and radii of the circles or spheres. Accurate localization can,for example, assist in the efficient allocation of network resources,the provision of location based services, and can provide additionaladvantages. In conventional networks, APs can be used for localization;however, the use of existing APs has several potential challenges.

It will be understood that, while 2 dimensional positioning requires atleast three non-collinear APs, a particular geometry having threenon-collinear APs may not be available in an existing deployment.Accurate localization using RTT ranging can require that APs haveconsistent processing delays with low variance. However, APs withadequate resources for localization may not be available in alldeployment scenarios. Further, heavy loading on a given AP such asprocessing a large memory transfer via direct memory addressing (DMA)may cause variation in the RTT turn-around time and thus degradelocalization accuracy and stability. Still further, contention may arisebetween the localization traffic and the normal data/control traffic ifusing a deployed AP for localization, leading to delay or loss oflocalization data. Still further, localization may require configurationor updates to the software/firmware on the AP so as to enable thedelivery of network geometry, map URIs or other information. Howeversuch configuration and updating may not be possible in all deploymentscenarios.

Using RTT measurement techniques to accurately determine positiontypically involves knowledge of time delays incurred by the wirelesssignals as they propagate through various devices comprising thenetwork. In practice, when employing conventional RTT positioningtechniques, estimating processing delay times may involve extensiveadditional software at both the STA and the AP to characterize andinterpret RTT processing delays, hardware changes in the wireless APs,and time-consuming pre-deployment fingerprinting and calibration of theoperational environment.

Accordingly, when using RTT techniques for position determination, itmay be desirable to avoid hardware changes in wireless access points orto avoid substantial additional processing so as to improve the positionlocation accuracy and performance in a cost-efficient manner.

SUMMARY

Exemplary In accordance with certain aspects, a mobile station may beprovided which comprises a transceiver and a processing unit, whereinthe processing unit may be configured to determine a first round-triptime (RTT) for a first measurement related communication between thetransceiver and a first network device, wherein the first RTT comprisesa uniform delay of time applied during the first measurement relatedcommunication by the first network device; determine a second RTT for asecond measurement related communication between the transceiver and asecond network device, wherein the second RTT comprises the uniformdelay of time applied during the second measurement relatedcommunication by the second network device; and determine, at least inpart, a position of the mobile station with regard to at least the firstand second network devices based, at least in part, on the first RTT andthe second RTT.

In accordance with certain aspects, an apparatus may be provided for usein a mobile station, the apparatus may comprise: means for determining afirst round-trip time (RTT) for a first measurement relatedcommunication between the transceiver and a first network device,wherein the first RTT comprises a uniform delay of time applied duringthe first measurement related communication by the first network device;means for determining a second RTT for a second measurement relatedcommunication between the transceiver and a second network device,wherein the second RTT comprises the uniform delay of time appliedduring the second measurement related communication by the secondnetwork device; and means for determining, at least in part, a positionof the mobile station with regard to at least the first and secondnetwork devices based, at least in part, on the first RTT and the secondRTT.

In accordance with certain aspects, a method for use at a mobile stationmay comprise: determining a first round-trip time (RTT) for a firstmeasurement related communication between the transceiver and a firstnetwork device, wherein the first RTT comprises a uniform delay of timeapplied during the first measurement related communication by the firstnetwork device; determining a second RTT for a second measurementrelated communication between the transceiver and a second networkdevice, wherein the second RTT comprises the uniform delay of timeapplied during the second measurement related communication by thesecond network device; and determining, at least in part, a position ofthe mobile station with regard to at least the first and second networkdevices based, at least in part, on the first RTT and the second RTT.

In accordance with certain aspects, a non-transitional computer-readablemedium having instructions stored therein may be provided, in which theinstructions are executable by a processing unit of a mobile station to:determine a first round-trip time (RTT) for a first measurement relatedcommunication between the transceiver and a first network device,wherein the first RTT comprises a uniform delay of time applied duringthe first measurement related communication by the first network device;determine a second RTT for a second measurement related communicationbetween the transceiver and a second network device, wherein the secondRTT comprises the uniform delay of time applied during the secondmeasurement related communication by the second network device; anddetermine, at least in part, a position of the mobile station withregard to at least the first and second network devices based, at leastin part, on the first RTT and the second RTT.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofembodiments of the invention and are provided solely for illustration ofthe embodiments and not limitation thereof.

FIG. 1 is a diagram illustrating an exemplary operating environment fora mobile station consistent with embodiments of the disclosure.

FIG. 2 is a block diagram illustrating various components of anexemplary mobile station.

FIG. 3 is a diagram illustrating an exemplary technique for determininga position of a mobile station using wireless access points.

FIG. 4 is a timing diagram illustrating timing for determining aposition of a mobile station using a plurality of wireless access pointsusing round trip time (RTT).

FIG. 5 is a diagram illustrating an operating environment for a mobilestation using exemplary appliances.

FIG. 6 is a timing diagram illustrating an exemplary timing fordetermining a position of a mobile station using appliances.

FIG. 7 is a block diagram illustrating various components of anexemplary appliance.

FIG. 8 is a flow chart illustrating an exemplary method for facilitatinglocalization using an appliance.

DETAILED DESCRIPTION

Aspects of the invention are disclosed in the following description andrelated drawings directed to specific embodiments of the invention.Alternate embodiments may be devised without departing from the scope ofthe invention. Additionally, well known elements of the invention willnot be described in detail or will be omitted so as not to obscure therelevant details of the invention.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. Likewise, the term “embodiments ofthe invention” does not require that all embodiments of the inventioninclude the discussed feature, advantage or mode of operation.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of embodiments ofthe invention. As used herein, the singular forms “a”, “an” and “the”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises”, “comprising,”, “includes” and “including”, when usedherein, specify the presence of stated features, integers, steps,operations, elements, and components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components, and groups thereof.

The methodologies described herein may be implemented by various meansdepending upon the application. For example, these methodologies may beimplemented in hardware, firmware, software, or any combination thereof.For a hardware implementation, the processing units may be implementedwithin one or more application specific integrated circuits (ASICs),digital signal processors (DSPs), digital signal processing devices(DSPDs), programmable logic devices (PLDs), field programmable gatearrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, other electronic units designed toperform the functions described herein, or a combination thereof.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a memory and executed by a processing unit. Memory may beimplemented within the processing unit or external to the processingunit. As used herein the term “memory” refers to any type of long term,short term, volatile, nonvolatile, or other memory and is not to belimited to any particular type of memory or number of memories, or typeof media upon which memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or code on a computer-readable medium.Examples include computer-readable media encoded with a data structureand computer-readable media encoded with a computer program.Computer-readable medium may take the form of an article of manufacture.Computer-readable media includes physical computer storage media. Astorage medium may be any available medium that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to store desired program code in the formof instructions or data structures and that can be accessed by acomputer; disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

In addition to storage on computer-readable medium, instructions and/ordata may be provided as signals on transmission media included in acommunication apparatus. For example, a communication apparatus mayinclude a transceiver having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessing units to implement the functions outlined in the claims. Thatis, the communication apparatus includes transmission media with signalsindicative of information to perform disclosed functions. At a firsttime, the transmission media included in the communication apparatus mayinclude a first portion of the information to perform the disclosedfunctions, while at a second time the transmission media included in thecommunication apparatus may include a second portion of the informationto perform the disclosed functions.

By way of brief summary and in accordance with various exemplaryembodiments, an exemplary round trip time appliance (RTT_APP) can beprovided that provides accurate and rapid localization of a station(STA) or that assists in improving existing localization measurements orestimates. The RTT_APP, by providing a limited number of dedicatedfunctions and a uniform processing delay, avoids many of the above notedissues, particularly those related to extensive processing needed todevelop estimates for AP based processing delays. The RTT_APP can, forexample, be configured to send ACKs in response to directed RTTmeasurement packets with no other processing functionality beingimplemented. The RTT_APP can be additionally configured to send beaconsif necessary for delivering information about the network. The RTT_APPcan operate on any one of, or a combination of multiple bands such as,for example, Wi-Fi 802.11 bands or the like. The RTT_APP may supportconfiguration to allow delivery of URIs for delivering network geometryor maps.

In accordance with various exemplary embodiments, the RTT_APP has anadvantageously low size, low cost and low power and requires lesshardware and software functionality than general-purpose access points.The RTT_APP need not support typical AP features such as routing,switching, bridging and the like and does not need extra ports such asEthernet, WAN, USB ports or the like. The RTT_APP need not support theadvanced software configuration required to enable different topologies,security profiles, VLANs and the like. The exemplary RTT_APP allows thedeployment of indoor positioning by replacing, or complementing existinginfrastructure that may not be deployed in a manner well suited forlocalization. While the RTT_APP is capable of sending occasional beaconsignals, since the RTT_APP is primarily configured to respond to RTTmeasurement requests, operation can be extended for long periods of timeon, for example, battery power, in a manner much more effectively than aconventional AP. Thus, an RTT_APP can be deployed where mainline powersources are not available. As will be further described herein below,the RTT_APP can provide all of the above noted and additional advantagesin a manner not previously contemplated.

FIG. 1 is a diagram of an exemplary operating environment 100 for a STA1108. Embodiments of the invention are directed to a RTT_APP that canassist STA1 108 to determine its position based upon round trip time(RTT) measurements where processing delays introduced by wireless accesspoints can be minimized or eliminated. It will be appreciated thatvarious embodiments address disadvantages associated with variations inthe processing delays among different access points. In addition tostatic differences in the processing delays among access points, thevariations may change over time due to load conditions and the like.Since positioning accuracy may be compromised by the differences inprocessing delay the need arises for eliminating variable processingdelays.

The operating environment 100 may contain one or more different types ofwireless communication systems and wireless positioning systems. In theembodiment shown in FIG. 1, a Satellite Positioning System (SPS) 102 maybe used as an independent source of position information for the STA1108. The STA1 108 may include one or more dedicated SPS receiversspecifically designed to receive signals for deriving geolocationinformation from the SPS satellites (102 a, 102 b, etc.).

It will be appreciated that, in general, an SPS may include a system oftransmitters positioned to enable entities to determine their locationon or above the Earth based, at least in part, on signals received fromthe transmitters. Such a transmitter typically transmits a signal markedwith a repeating pseudo-random noise (PN) code of a set number of chipsand may be located on ground based control stations, user equipmentand/or space vehicles. In a particular example, such transmitters may belocated on Earth orbiting satellite vehicles (SVs). For example, a SV ina constellation of Global Navigation Satellite System (GNSS) such asGlobal Positioning System (GPS), Galileo, Glonass or Compass maytransmit a signal marked with a PN code that is distinguishable from PNcodes transmitted by other SVs in the constellation (e.g., usingdifferent PN codes for each satellite as in GPS or using the same codeon different frequencies as in Glonass). In accordance with certainaspects, the techniques presented herein are not restricted to globalsystems (e.g., GNSS) for SPS. For example, the techniques providedherein may be applied to or otherwise enabled for use in variousregional systems, such as, e.g., Quasi-Zenith Satellite System (QZSS)over Japan, Indian Regional Navigational Satellite System (IRNSS) overIndia, Beidou over China, etc., and/or various augmentation systems(e.g., an Satellite Based Augmentation System (SBAS)) that may beassociated with or otherwise enabled for use with one or more globaland/or regional navigation satellite systems. By way of example but notlimitation, an SBAS may include an augmentation system(s) that providesintegrity information, differential corrections, etc., such as, e.g.,Wide Area Augmentation System (WAAS), European Geostationary NavigationOverlay Service (EGNOS), Multi-functional Satellite Augmentation System(MSAS), GPS Aided Geo Augmented Navigation or GPS and Geo AugmentedNavigation system (GAGAN), and/or the like. Thus, as used herein an SPSmay include any combination of one or more global and/or regionalnavigation satellite systems and/or augmentation systems, and SPSsignals may include SPS, SPS-like, and/or other signals associated withsuch one or more SPS.

The operating environment 100 may also include a plurality of one ormore types of Wide Area Network Wireless Access Points (WAN-WAPs) 104,which may be used for wireless voice and data communication, and asanother source of independent position information for STA1 108.Typically, each of the WAN-WAPs 104 a-104 c within the WWAN may operatefrom fixed positions, and provide network coverage over largemetropolitan and regional areas. The WAN-WAPs 104 may be part of awireless wide area network (WWAN), which may include cellular basestations at known locations, and other wide area wireless systems, suchas, for example, WiMAX nodes as specified under 802.16. It will beappreciated that the WWAN may include other known network componentswhich, for simplicity, are not shown in FIG. 1.

The operating environment 100 may further include Local Area NetworkWireless Access Points (LAN-WAPs) 106, which may be used for wirelessvoice and data communication, and as another independent source ofposition data. The LAN-WAPs 106 can be part of a Wireless Local AreaNetwork (WLAN), which may operate in buildings and performcommunications over smaller geographic regions than a WWAN. SuchLAN-WAPs 106 may be part of, for example, Wi-Fi networks such asnetworks specified for operation in accordance with 802.11x, cellularpiconets and femtocells, Bluetooth Networks, and the like.

The STA1 108 may derive position information from any one or acombination of the SPS satellites 102, the WAN-WAPs 104, and theLAN-WAPs 106. Each of the aforementioned systems can provide anindependent estimate of the position for STA1 108 using differenttechniques. In some embodiments, the mobile station may combine thesolutions derived from each of the different types of access points toimprove the accuracy of the position data. However, for increasedaccuracy, particularly within an indoor location where satellite signalsmay be difficult to receive, reliance on localization or trilaterationbased on signal sources closer in proximity to the STA1 108 results inthe potential for greater accuracy.

When deriving position using the SPS 102, the mobile station may use areceiver specifically designed for use with the SPS that extractsposition, using conventional techniques, from a plurality of signalstransmitted by SPS satellites 102. The method and apparatus describedherein may be used with various satellite positioning systems, such asthe United States Global Positioning System (GPS), the Russian Glonasssystem, the European Galileo system, any system that uses satellitesfrom a combination of satellite systems, or any satellite systemdeveloped in the future. Furthermore, the disclosed method and apparatusmay be used with positioning determination systems that use pseudolitesor a combination of satellites and pseudolites. Pseudolites areground-based transmitters that broadcast a PN code or other ranging codethat is similar to a GPS or CDMA cellular signal and is modulated on anL-band or other frequency carrier signal, which may be synchronized withGPS time. Each such pseudolite transmitter may be assigned a unique PNcode so as to permit identification by a remote receiver. Pseudolitesare useful in situations where GPS signals from an orbiting satellitemight be unavailable, such as in tunnels, mines, buildings, urbancanyons or other enclosed areas. Another implementation of pseudolitesis known as radio-beacons. The term “satellite”, as used herein, isintended to include pseudolites, equivalents of pseudolites, andpossibly others. The term “SPS signals”, as used herein, is intended toinclude SPS-like signals from pseudolites or equivalents of pseudolites.

When deriving position from the WWAN, each WAN-WAPs 104 a-104 c may takethe form of base stations within a digital cellular network, and theSTA1 108 may include a cellular transceiver and processing unit that canexploit the base station signals to derive position. Such cellularnetworks may include, but are not limited to, standards in accordancewith GSM, CMDA, 2G, 3G, 4G, LTE, and the like. It should be understoodthat the digital cellular network may include additional base stationsor other resources shown in FIG. 1. While WAN-WAPs 104 may actually bemovable or otherwise capable of being relocated, for illustrationpurposes it will be assumed that they are essentially arranged in afixed position.

The STA1 108 may perform position determination using known time ofarrival techniques such as, for example, Advanced Forward LinkTrilateration (AFLT). In other embodiments, each WAN-WAP 104 a-104 c maytake the form of a WiMAX wireless networking base station. In such acase, the STA1 108 may determine its position using time-of-arrival(TOA) techniques from signals provided by the WAN-WAPs 104. The STA1 108may determine positions either in a stand alone mode, or using theassistance of a positioning server 110 and network 112 using TOAtechniques, as will be described in more detail below. Note thatembodiments of the disclosure include having the STA1 108 determineposition information using WAN-WAPs 104 which are of different types.For example, some WAN-WAPs 104 may be cellular base stations, and otherWAN-WAPs may be WiMAX base stations. In such an operating environment,the STA1 108 may be able to exploit the signals from each different typeof WAN-WAP, and further combine the derived position solutions toimprove accuracy.

When deriving position using the WLAN, the STA1 108 may use time ofarrival techniques with the assistance of the positioning server 110 andthe network 112. The positioning server 110 may communicate to themobile station through network 112. Network 112 may include acombination of wired and wireless networks which incorporate theLAN-WAPs 106. In one embodiment, each LAN-WAP 106 a-106 e may be, forexample, a wireless access point, which is not necessarily set in afixed position and can change location. The position of each LAN-WAP 106a-106 e may be stored in the positioning server 110 in a commoncoordinate system. In one embodiment, the position of the STA1 108 maybe determined by having the STA1 108 receive signals from each LAN-WAP106 a-106 e. Each signal may be associated with its originating LAN-WAPbased upon some form of identifying information that may be included inthe received signal such as, for example, a MAC address. The STA1 108may then derive the time delays associated with each of the sortedreceived signals. The STA1 108 may then form a message which can includethe time delays and the identifying information of each of the LAN-WAPs,and send the message via network 112 to the positioning server 110.Based upon the received message, the positioning server may thendetermine a position, using the stored locations of the relevantLAN-WAPs 106, of the STA1 108. The positioning server 110 may generateand provide a Location Configuration Indication (LCI) message to theSTA1 108 that includes a pointer to the position of the mobile stationin a local coordinate system. The LCI message may also include otherpoints of interest in relation to the location of the STA1 108. LCI mayfirst be established simply as a result of server 110 knowing the MACaddresses of nearby LAN-WAPs that the STA 108 can see. Along with theLCI, the positions of the nearby LAN-WAPs are given to the STA 108whereupon the STA 108 can derive its position using the nearby LAN-WAPspositions. Alternatively, server 110 may generate an LCI that includesthe STA position. It should be noted that the position of STA 108 can bederived at server 110 or at the STA 108. When deriving position at theSTA 108, server 110 provides an LCI with the positions of LAN-WAPs asdescribed. When computing the position of the STA1 108, the positioningserver 110 may take into account the different delays which can beintroduced by elements within the wireless network.

The position determination techniques described herein may be used forvarious wireless communication networks such as a wireless wide areanetwork (WWAN), a wireless local area network (WLAN), a wirelesspersonal area network (WPAN), and so on. The terms “network” and“system” may be used interchangeably. A WWAN may be a Code DivisionMultiple Access (CDMA) network, a Time Division Multiple Access (TDMA)network, a Frequency Division Multiple Access (FDMA) network, anOrthogonal Frequency Division Multiple Access (OFDMA) network, aSingle-Carrier Frequency Division Multiple Access (SC-FDMA) network, aLong Term Evolution (LTE) network, a WiMAX (IEEE 802.16) network, and soon. A CDMA network may implement one or more radio access technologies(RATs) such as cdma2000, Wideband-CDMA (W-CDMA), and so on. Cdma2000includes IS-95, IS-2000, and IS-856 standards. A TDMA network mayimplement Global System for Mobile Communications (GSM), DigitalAdvanced Mobile Phone System (D-AMPS), or some other RAT. GSM and W-CDMAare described in documents from a consortium named “3rd GenerationPartnership Project” (3GPP). Cdma2000 is described in documents from aconsortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPPand 3GPP2 documents are publicly available. A WLAN may be an IEEE802.11x network, and a WPAN may be a Bluetooth network, an IEEE 802.15x,or some other type of network. The techniques may also be used for anycombination of WWAN, WLAN and WPAN.

The block diagram of FIG. 2 illustrates various components of anexemplary mobile station 200 (e.g., STA1 108 of FIG. 1). For the sake ofsimplicity, the various features and functions illustrated in the boxdiagram of FIG. 2 are connected together using a common bus which ismeant to represent that these various features and functions areoperatively coupled together regardless of the specific coupling means.Aside from a common bus connection, those skilled in the art willrecognize that other connections, mechanisms, features, functions, orthe like, may be provided and adapted as necessary to operatively coupleand configure an actual portable wireless device. Further, it is alsorecognized that one or more of the features or functions illustrated inthe example of FIG. 2 may be further subdivided or two or more of thefeatures or functions illustrated in FIG. 2 may be combined.

As used herein, a mobile station (MS) refers to a device such as acellular or other wireless communication device, personal communicationsystem (PCS) device, personal navigation device (PND), PersonalInformation Manager (PIM), Personal Digital Assistant (PDA), laptop orother suitable mobile device which is capable of receiving wirelesscommunication and/or navigation signals. The term “mobile station” isalso intended to include devices which communicate with a personalnavigation device (PND), such as by short-range wireless, infrared,wireline connection, or other connection—regardless of whether satellitesignal reception, assistance data reception, and/or position-relatedprocessing occurs at the device or at the PND. Also, “mobile station” isintended to include all devices, including wireless communicationdevices, computers, laptops, etc. which are capable of communicationwith a server, such as via the Internet, Wi-Fi, or other network, andregardless of whether satellite signal reception, assistance datareception, and/or position-related processing occurs at the device, at aserver, or at another device associated with the network. Any operablecombination of the above are also considered a “mobile station.”

The mobile station 200 may include one or more wide area networktransceiver(s) 204 that may be connected to one or more antennas 202.The wide area network transceiver 204 can include suitable devices,hardware, and software for communicating with and detecting signalsto/from WAN-WAPs 104, and directly with other wireless devices within anetwork. In one aspect, the wide area network transceiver 204 mayinclude a CDMA communication system suitable for communicating with aCDMA network of wireless base stations. However, in other aspects, thewireless communication system may include a different type of cellulartelephony technology, such as, for example, a TDMA or GSM network, orthe like. Additionally, any other type of wireless networkingtechnologies may be used, for example, WiMAX in accordance with the802.16 standard, and the like. The mobile station 200 may also includeone or more local area network transceivers 206 that may be connected toone or more antennas 202. The local area network transceiver 204includes suitable devices, hardware, and software for communicating withand detecting signals to/from LAN-WAPs 106, and directly with otherwireless devices within a network. In one aspect, the local area networktransceiver 206 may include a Wi-Fi communication system, for example inaccordance with the 802.11x standard, suitable for communicating withone or more wireless access points. However in other aspects, the localarea network transceiver 206 can include another type of local areanetwork technology, personal area network technology, such as aBluetooth network, or the like. Additionally, any other type of wirelessnetworking technologies may be used, for example, Ultra Wide Band,ZigBee, wireless USB, or the like.

As used herein, the abbreviated term “wireless access point” (WAP) mayrefer to LAN-WAPs 106 and WAN-WAPs 104. Specifically, in the descriptionpresented below, when the term “WAP” is used, it should be understoodthat embodiments may include a mobile station 200 that can exploitsignals from a plurality of LAN-WAPs 106, a plurality of WAN-WAPs 104,or any combination of the two. The specific type of WAP being used bythe mobile station 200 may depend upon the environment of operation.Moreover, the mobile station 200 may dynamically select between thevarious types of WAPs in order to arrive at an accurate positionsolution.

An SPS receiver 208 may also be included in mobile station 200. The SPSreceiver 208 may be connected to the one or more antennas 202 forreceiving satellite signals. The SPS receiver 208 may comprise anysuitable hardware and software for receiving and processing SPS signals.The SPS receiver 208 requests information and operations as appropriatefrom the other systems, and performs the calculations necessary todetermine the position of mobile station 200 using measurements obtainedby any suitable SPS algorithm.

It should be noted that in some embodiments, a relative motion sensor212 may be coupled to processing unit 210 to provide relative movementand orientation information independently of motion data derived fromsignals received by the wide area network transceiver 204, the localarea network transceiver 206 and the SPS receiver 208.

By way of example but not limitation, relative motion sensor 212 may usean accelerometer, such as a MEMS device, a gyroscope, a geomagneticsensor such as a compass, an altimeter such as a barometric pressurealtimeter, and any other type of movement detection sensor. Moreover,relative motion sensor 212 may include a plurality of different types ofdevices and combine their outputs in order to provide motioninformation. For example, relative motion sensor may use a combinationof a multi-axis accelerometer and orientation sensors to provide theability to compute positions in 2-D and 3-D coordinate systems.

A processing unit 210 may be coupled to the wide area networktransceiver 204, local area network transceiver 206, the SPS receiver208 and the relative motion sensor 212. The processing unit may includeone or more microprocessors, microcontrollers, and digital signalprocessors that provide processing functions, as well as othercalculation and control functionality. The processing unit 210 may alsoinclude or be otherwise coupled to a memory 214 for storing data andsoftware instructions for executing programmed functionality within themobile station. The memory 214 may be on-board the processing unit 210,such as within the same IC package, or the memory may be external memoryto the processing unit and functionally coupled over a data bus or thelike, or a combination of internal and external memory. The details ofsoftware functionality associated with aspects of the disclosure will bediscussed in more detail below.

A number of software modules and data tables may reside in memory 214and be used by the processing unit 210 in order to manage bothcommunications and positioning determination functionality. Asillustrated in FIG. 2, memory 214 may include and otherwise receive awireless-based positioning module 216, an application module 218, areceived signal strength indicator (RSSI) module 220, a round trip time(RTT) module 222, and a relative positioning module (not shown). Itshould be appreciated that the organization of the memory contents asshown in FIG. 2 is merely exemplary, and as such the functionality ofthe modules and data structures may be combined, separated, and bestructured in different ways depending upon the implementation of themobile station 200.

The application module 218 may be a process running on the processingunit 210 of the mobile station 200, which requests position informationfrom the wireless-based positioning module 216. Alternatively, theposition information may be provided continuously, periodically, or thelike by positioning module 216, either autonomously or under the controlof the application module 218. Applications typically run within anupper layer of a communications architecture model, such as theApplication Layer of the open systems interconnect (OSI) seven layerOpen Architecture protocol model, and may include Indoor Navigation,Buddy Locator, Shopping and Coupons, Asset Tracking, location-awareService Discovery and the like. The wireless-based positioning module216 may derive the position of the mobile station 200 using informationderived from the RTTs measured from signals exchanged with a pluralityof WAPs. In order to accurately determine position using RTT techniques,reasonable estimates of processing time delays introduced by each WAPmay be used to calibrate/adjust the measured RTTs. The measured RTTs maybe determined by the RTT module 222, which can measure the timings ofsignals exchanged between the mobile station 200 and the WAPs to deriveRTT information.

Once measured, the RTT values may be passed to the wireless-basedpositioning module 216 to assist in determining the position of themobile station 200. The wireless-based positioning module 216 may usethe amplitude values of the signals transmitted by the WAPs to assist inthe estimation of the processing times of the WAPs. These amplitudevalues may be determined in the form of RSSI measurements determined byRSSI module 220. The RSSI module 220 may provide amplitude andstatistical information regarding the signals to the wireless-basedpositioning module 216. The wireless-based positioning module 216 usethe RTT measurements to accurately determine position based onpropagation delay measurements and the like as will be further describedherein below.

Without the effects associated with reducing and making uniform theprocessing delay as provided, for example, by the RTT_APP as discussedand described herein, additional calibration would be required tofurther refine the processing times of the WAPs using informationobtained, for example, by the relative motion sensor 212 or othersections. In one embodiment, the relative motion sensor 212 may directlyprovide position and orientation data to the processing unit 210, whichmay be stored, for example, in memory 214. In other embodiments, therelative motion sensor 212 may provided data which should be furtherprocessed by processing unit 210 to derive information to perform thecalibration. For example, the relative motion sensor 212 may provideacceleration and orientation data (single or multi-axis).

The position may be output to the application module 218, such as inresponse to request or in a continuous manner. In addition, thewireless-based positioning module 216 may use a parameter database 224for exchanging operational parameters. Such parameters may include thedetermined processing times for each WAP, the WAPs positions in a commoncoordinate frame, various parameters associated with the network,initial processing time estimates, and the like. Details of theparameters will be provided in subsequent sections below.

In other embodiments, the additional information may optionally includeauxiliary position and motion data which may be determined from othersources besides the relative motion sensor 212, such as, for example,from SPS measurements. The auxiliary position data may be intermittentand noisy, but may be useful as another source of independentinformation for estimating or confirming estimates of the positioning ofthe WAPs, or for estimating or confirming other information associatedwith positioning, depending upon the environment in which the mobilestation 200 is operating.

While the modules shown in FIG. 2 are illustrated in the example asbeing contained in memory 214, it is recognized that in certainimplementations such procedures may be provided for or otherwiseoperatively arranged using various mechanisms. For example, all or partof wireless-based positioning module 216 and application module 218 maybe provided in firmware. Additionally, while in the present example,wireless-based positioning module 216 and application module 218 areillustrated as being separate features, it is recognized, for example,that such procedures may be combined together as one procedure orperhaps with other procedures, or otherwise further divided into aplurality of sub-procedures. Each of the various alternate and/oradditional configurations may be encompassed as a means for performingvarious inventive functions as further described herein below.

Processing unit 210 may include any form of logic suitable forperforming at least the techniques provided herein. For example,processing unit 210 may be operatively configurable based oninstructions in memory 214 to selectively initiate one or more routinesthat exploit motion data for use in other portions of the mobilestation.

The mobile station 200 may include a user interface 250 which providesany suitable interface systems, such as a microphone/speaker 252, keypad254, and display 256 that allows user interaction with the mobilestation 200. The microphone/speaker 252 can provide for voicecommunication services using the wide area network transceiver 204 andthe local area network transceiver 206. The keypad 254 can include anytype of keypad containing any suitable buttons for user input. Thedisplay 256 comprises any suitable display, such as, for example, abacklit LCD display, and may further include a touch screen display foradditional user input modes.

As used herein, STA1 108 may be any portable or movable device ormachine that is configurable to acquire wireless signals transmittedfrom, and transmit wireless signals to, one or more wirelesscommunication devices or networks. As shown in FIG. 1 and FIG. 2, themobile station is representative of such a portable wireless device.Thus, by way of example but not limitation, STA1 108 may include a radiodevice, a cellular telephone device, a computing device, a personalcommunication system (PCS) device, or other like movable wirelesscommunication equipped device, appliance, or machine.

As used herein, the term “wireless device” may refer to any type ofwireless communication device which may transfer information over anetwork and also have position determination and navigationfunctionality. The wireless device may be any cellular mobile terminal,personal communication system (PCS) device, personal navigation device,laptop, personal digital assistant, or any other suitable mobile stationcapable of receiving and processing network and SPS signals forwireless-based position determination.

Wireless-based position determination may be accomplished in a varietyof ways using separate signal sources or a combination thereof. In someembodiments, wireless position determination may be performed using SPSmeasurements. For example, if the STA1 108 has just entered an indoorenvironment, and if the indoor environment does not severely attenuateSPS signals, SPS positioning may be used. In other embodiments,techniques using signals employed for voice/data communication may beexploited for position determination. Various techniques in thiscategory are set forth in the co-pending application entitled “WIRELESSPOSITION DETERMINATION USING ADJUSTED ROUND TRIP TIME MEASUREMENTS”(U.S. patent application Ser. No. 12/622,289).

A simplified environment is shown in FIG. 3 for illustrating anexemplary technique for determining a position of STA1 108. The STA1 108may communicate wirelessly with, for example, a plurality of WAPs 311using RF signals such as 2.4 GHz signals, and standardized protocols forthe modulation of the RF signals and the exchanging of informationpackets configured according to standards such as IEEE 802.11 and thelike. By extracting different types of information from the exchangedsignals, and using the layout of the network, such as the networkgeometry as described below, the STA1 108 may determine its position ina predefined reference coordinate system. As shown in FIG. 3, the mobilestation may specify its position (x_(t), y_(t)) using a two-dimensionalcoordinate system; however, embodiments disclosed herein are not solimited, and may also be applicable to determining positions using, forexample, a three-dimensional coordinate system, if an extra dimension isdesired. Additionally, while only three WAPs, WAP1 311 a, WAP2 311 b,and WAP3 311 c, are shown in FIG. 3, it may be desirable to useadditional WAPs and solve for position using techniques applicable toover-determined systems, which can average out various errors introducedby different noise effects, and thus improve the accuracy of thedetermined position.

In order to determine a position (x_(t), y_(t)) for a given time t usingwireless signal measurements, the mobile station STA1 108 may first needto determine the network geometry. The network geometry can include thepositions of each WAP 311 in a reference coordinate system designated bycoordinates (x_(k), y_(k)), where k=1, 2, 3 corresponding to locations(x1, y1) for WAP1 311 a, (x2, y2) for WAP2 311 b, and (x3, y3) WAP3 311c as shown in FIG. 3. The mobile station may then determine a distanced_(k), where k=1, 2, 3, corresponding to d1 between STA 108 and WAP1 311a, d2 between STA1 108 and WAP2 311 b, and d3 between STA 108 and WAP311 c. As will be described in more detail below, a number of differentapproaches can be used to estimate these distances (d_(k)), such as byknowledge of characteristics of the RF signals exchanged between theSTA1 108 and each WAP 311. Such characteristics may include, as will bediscussed below, the round trip propagation time of the signals, and thestrength of the signals according to the RSSI. The distances are furthersubject to various errors 312 a-312 c, designated as err_(dk), wherek=1, 2, 3. Of particular interest in the present disclosure is the errorattributable to processing delay of the WAPs. Eliminating significantprocessing delays, and in particular, variations in the processingdelays among WAPs will be described in greater detail herein below.

In other embodiments, the distances (d_(k)) may in part be determined orrefined using other sources of information that are not associated withthe WAPs. For example, other positioning systems, such as SPS, may beused to provide a rough estimate of d_(k). It should be noted that it islikely that SPS may have insufficient signal in the anticipatedoperating environments such as indoors, metropolitan area, or the like,to provide a consistently accurate estimate of d_(k). However SPSsignals may be combined with other information to assist in the positiondetermination process. Other relative positioning devices may reside inthe STA1 108 which can be used as a basis to provide rough estimates ofrelative position and direction.

Once each distance is determined, the mobile station can then solve forits position (x_(t), y_(t)) by using a variety of known geometrictechniques, such as, for example, trilateration. From FIG. 3, it can beseen that the position of the STA1 108 ideally lies at the intersectionof dotted circles surrounding each WAP. The circles can be defined byradius d_(k) and center (x_(k), y_(k)), where k=1, 2, 3. In practice,due to noise, various systematic and random factors and other errors inthe networking system, including load based processing delay in eachWAP, the intersection of these circles may not lie at a single point.

To better understand the issues associated with location calculationusing, for example, RTT measurement, the sections below will discuss ingreater detail wireless-based position determination according to RTTmeasurements, including RTT measurements with uniform delay associatedwith an RTT_APP in accordance with various exemplary embodiments. Itwill be appreciated that RTT and RSSI measurements can be combined toimprove the estimate of the processing time delays for each WAP 311.

Referring again to FIG. 3, determining the distance between the STA1 108and each WAP 311 may involve using the propagation time informationassociated with the RF signals. In one embodiment, determining the roundtrip time (RTT) of signals exchanged between the STA1 108 and a WAP 311can be performed and converted to a distance (d_(k)). RTT techniques canbe used to measure the time between sending a data packet and receivingan acknowledgement. The RTT measurement methods generally usecalibration to remove processing delays. However, it may be insufficientto use calibration when attempting to provide high degrees of positionaccuracy, particularly in applications with high demand for locationprecision. While in some applications and environments, the processingdelays for the mobile station and the wireless access points are assumedto be the same, in reality, they are often different by varying degreesover time.

To measure the RTT with respect to a given WAP 311, as shown in FIG. 4,the STA1 108 may send a probe request 410, such as a directed proberequest, which is capable of being received by WAP 311, and possiblyother WAPs that are operating and within receiving range. The time theprobe request 410 was sent, such as a transmit time t_(TX) for thepacket can be recorded. After the corresponding propagation time t_(P0)from the STA1 108 to WAP 311, which time can be generalized as t_(PN)442, the WAP will receive the packet. WAP 311 may then process thedirected probe request 410 and send an ACK, such as ACK 411 back to theSTA1 108 after a processing time, such as Δ_(WAP0) 431, or in thegeneralized case, Δ_(WAPN) 441. After a second propagation time t_(P0),the STA1 108 may record the time the ACK packet was received such as areceive time t_(RX) ACK. The mobile station may then determine the RTTas time 420, or in the generalized case, time 429, based on, forexample, the time difference t_(RX) ACK−t_(TX) Packet. More simply, theRTT is equal to twice the propagation delay plus the processing delay.

By using directed probe request-based RTT ranging as described above,the STA1 108 can perform RTT measurement without directly associatingwith WAP 311. Since a directed access probe is considered a unicastpacket, WAP 311 may typically ACK a successful decoding of an accessprobe packet after a prescribed period of time. By avoiding associatingwith WAP 311, extra overhead can be greatly reduced.

The round-trip time between the STA1 108 and WAP k may be modeled asfollows in EQ. 1.

RTT _(k)=2d _(k)+Δ_(k)+Δ_(STA) +n _(k)  (1)

where:

d_(k) is the actual distance between the STA1 108 and WAP_(k) 311 (ft);

Δ_(k) is the hardware processing time of the WAP_(k) 311 (ns);

Δ_(STA) is the hardware processing delay at the STA1 108 (ns); and

n_(k) is the error in the RTT measurement (ns), which is the sum of theerrors due to unknown WAP height, mobile station timing errors, and WAPtiming errors.

It should be appreciated that because the units of distance are providedin feet, and the units of time are provided in nano-seconds, thevelocity of light may be approximated as unity to simplify the model andreduce computation time by avoiding multiply operations.

It may be assumed that the STA processing delay Δ_(STA) can becalibrated out by the STA1 108, particularly for fixed processing delay.Thus Δ_(STA) can be taken as zero. If the STA1 108 knows the processingtime Δ for individual WAP_(k) 311, the propagation time to the WAP_(k)311 can be estimated as (RTT_(k)−Δ_(k))/2, which will correspond to thedistance (d_(k)) between the STA1 108 and the WAP_(k) 311. However, theSTA1 108 typically has no knowledge of the processing time of theWAP_(k) 311, and the STA1 108 typically must obtain an estimate of theprocessing time Δ_(k) before the distance to the WAP_(k) 311 can beestimated. However, the WAP processing delay Δ_(k) can be variable fromone individual WAP to another or at least may contain a variable delaycomponent and thus may be difficult to calibrate out, particularly asnon-RTT measurement related processing load increases or decreases forindividual WAPs. Various exemplary embodiments of a RTT_APP as discussedand described herein are designed to alleviate the error associated withvariable processing times.

In addition to estimation involving RTT, it should be noted that thedistance between each WAP 311 and the STA1 108 may also be estimated, oran RTT-based estimate may be improved or confirmed using otherinformation. In one embodiment, the additional information may include areceived signal strength indication (RSSI) or measurement associatedwith the ACK packets received from each WAP 311.

Even though the delay in the RTT_APP may be minimal and fixed, from oneRTT_APP to another, it may be necessary or desirable for a capability toestimate delays, for example, in non-RTT_APP devices, and to confirm theprocessing time, however negligible, for the RTT_APP. For suchestimations, the RSSI approach can be used. For RSSI-based estimation,the STA1 108 may use an approximate model of distance and variance inthe distance as a function of the signal strength (RSSI). The RSSI modelmay be used when the STA1 108 is initially trying to learn the WAPprocessing delays. One feature of the RTT-based positioning algorithm isthat the RSSI model can be extremely simple, without the need forextensive pre-deployment fingerprinting. However, in an environmentwhere RTT_APPs are present, RSSI estimation may be optionally eliminatedto save processing resources at the STA1 108.

In an embodiment, the RSSI model may assume that the only RSSIinformation known to the mobile station is the approximate maximumdistance d_(max), in feet, as a function of RSSI in dBm. Based oninitial propagation simulations for an indoor environment with WAPshaving a maximum range of 225 feet, the function is provided below inEQ. 2.

$\begin{matrix}{{d_{\max}({RSSI})} = {\min \left( {10^{\frac{- {({{RSSI} + 25.9})}}{20.0}},225} \right)}} & (2)\end{matrix}$

From the above distance bound, the STA1 108 may convert any measuredRSSI to a distance estimate that may be modeled as normally distributedwith the following relationships in EQ. 3 and EQ. 4:

$\begin{matrix}{d_{RSSI} = \frac{d_{\max}({RSSI})}{2}} & (3) \\{\sigma_{d_{RSSI}}^{2} = \frac{d_{\max}^{2}({RSSI})}{16}} & (4)\end{matrix}$

where the variance assumes that 4σ_(dRSSI)=d_(max).

The following description provides details for a mobile station-centricalgorithm for position determination based upon from RTT and otheradditional measurements, which may include RSSI measurements. In anembodiment, the STA1 108 may estimate its distance to wireless accesspoints, each having positions which are known to the STA1 108 usingtechniques described above. Using these distance estimates and thelocations of the wireless access points 311, the STA1 108 can determineits position. It is assumed that the position of each wireless accesspoint is known in a standard coordinate system, such as WGS-84 used inGPS.

Once the RSSI measurements are performed, a set of distances to each WAPmay be determined using RSSI measurements to arrive at RSSI distances byRSSI module 220 (FIG. 2). Once the RSSI distances are determined, thedistances between the mobile station and each WAP_(k) 311 may bedetermined using the RTT measurements, which can be referred to as RTTdistances, by RTT module 222 (FIG. 2). The RSSI distances and RTTdistances may be provided to a wireless-based positioning module 216(FIG. 2), where they can be combined using conventional trilaterationtechniques to determine the mobile station position. Once the STA1 108position is determined, the processing time for each WAP 311 may beconfirmed or updated based upon the determined position. Techniques forcombining the RTT and RSSI measurements may be based on minimum meansquare error techniques. It should be noted that in accordance with anembodiment, a given WAP can identify itself as a RTT_APP, which shouldalert the STA1 108 that estimation of processing delay using RSSI andthe like may be unnecessary for that particular WAP. Alternatively, RTTmeasurements performed based on ACKs generated by an RTT_APP can beconfirmed using RSSI distance estimations for accuracy confirmation orchecking.

It will also be appreciated that the position estimations may further berefined, even if generated by RTT_APP-based RTT measurements, by usinginformation obtained from, for example, the relative motion sensor 212(FIG. 2) to refine a position of a mobile station and adjust theprocessing time delay for each regular (non-RTT_APP) WAP or, forconfirmation, for RTT_APPs.

FIG. 5 is a diagram that shows an exemplary environment 500 thatincludes RTT_APP0 501 a-RTT_APP2 501 c for providing ACKs based on, forexample, a known, uniform processing delay to establish or assist inestablishing an accurate estimate of the position of the STA1 108.Moreover, the embodiment illustrates that the RTT_APPs can be located inthe positioning environment either alone or with other access devicessuch as LAN-WAPs, WAN-WAPs and satellite terminals as described inconnection with FIG. 1.

In an embodiment, RTT_APP 501 can provide a specialized acknowledgement,in the form of a response or acknowledgement, which is referred to inFIG. 6 as RTT_MEAS_RESP_APP0 611, in response to a directed proberequest, referred to in FIG. 6 as RTT_MEAS_REQ 610. Since the processingdelay for each RTT_APP is known to be negligible or uniform, the termΔ_(k) can be made a constant and advantageously factored out of EQ (1)above. It will be appreciated that removal of Δ_(k) from EQ (1) isparticularly advantageous since other factors are susceptible ofdetermination without generating estimates. For example, the processingdelay Δ_(STA) of STA1 108 can be easily determined by the mobile stationitself. By substituting a known value of ΔRTT_APP (processing delay forRTT_APP) for the processing delay Δ_(k), or by eliminating Δ_(k) byassuming a constant value near zero, the accuracy and the simplicity ofthe positioning estimates derived according to EQ (1) can be drasticallyincreased. It will be appreciated that in an average environment, a onenano-second error in the RTT calculation can result in one-half foot ofranging error. Thus, processing delay variations of severalmicro-seconds could result in a large degree of error, which isunacceptable for many applications.

To better appreciate the advantages, reference is made to FIG. 6 wheretiming relationships are shown in a manner similar to that of FIG. 4.STA1 108 can be configured to send a probe request and/or a directedprobe request, which for illustrative purposes is labeled RTT_MEAS_REQ610. It will be appreciated that in some embodiments, the request cancontain sufficient identifying characteristics that it will berecognized only by appliances, such as RTT_APPs. Alternatively, therequest can be sent as a normal probe signal at which point any WAP canrespond with an ACK. In such an embodiment, the appliances can eitheridentify themselves as RTT_APPs or they can simply respond, and STAT1108 can be configured in advance to know which of the WAPs in theenvironment are designated as RTT_APPs. Even in a scenario where nospecial identification is provided regarding the existence of RTT_APPsin the environment, the mere presence of the RTT_APP should improve theaccuracy of the measurements by proving consistently accurate resultsmeaning that STAT1 108 will be able to consistently confirm themeasurement results associated with the RTT_APPs.

When the RTT_MEAS_REQ 610 is received, for example at RTT_APP0 501, anacknowledgement can be immediately generated, which for illustrativepurposes is labeled as RTT_MEAS_RESP_APP0 611. It will be appreciatedthat the RTT_APP processing time Δ_(RTT) _(—) _(APP) 620 can be assumedto be uniform among the different RTT_APPs in the environment such asRTT_APP0 501, simplifying the calculation for determining the positionof STA1 108 while reducing the amount of variable error. From the timeof sending the RTT_MEAS_REQ 610, the round trip time can be Δ_(RTT) _(—)_(APP) 620+RTT 621 for RTT_APP0 501.

In order to provide accuracy in connection with position estimates ofSTA1 108 in an environment, wireless round trip measurement appliances,RTT_APPs, can be provided that will respond to probes or directed probeswith an ACK signal and, in some embodiments, with additional informationthat could include location coordinates in (x,y) form or other form aswould be understood and appreciated. The RTT_APP can be dedicated toresponding only to directed requests and thus can be provisionedminimally without, for example, routing capabilities or the like thatwould be associated with a WAP.

An exemplary structure for an RTT_APP is illustrated in FIG. 7. ARTT_APP unit 701, which can be a dedicated appliance for acknowledgingdirected probes or requests such as RTT_MEAS_REQ 610 or the like, can beprovided with basic components such as a media access control (MAC)block 710, a physical layer (PHY) block 720, and a radio frequency (RF)block 730. It will be appreciated that while the blocks are shown asseparate, some or all of the MAC block 710, PHY block 720 and RF block730 can be integrated together in the same module, unit, cell or thelike, such as module 715. In particular, it will be appreciated that thePHY block 720 can incorporate the RF block 730, and in some cases theMAC block 710. In other embodiments, parts of the blocks may overlap, aswill be understood. While it is appreciated that the distribution of thefunctionality can be flexible, MAC block 710 should be hardware basedand as simple as possible since the primary task of MAC block 710 is torespond to the RTT probe request. If beaconing is supported, the MACblock 710 should also perform functions such as carrier sense and mediumaccess in accordance with 802.11 standards, but such standards supportcan be provided in a significantly simplified manner compared to a fullfeatured access point which would need to support several featuresrelated to security, turbo modes, packet aggregation and the like. Ifbeaconing is supported, the automatic response may include a beaconframe, and the MAC block 710 may implement one of a carrier sensemechanism and a back-off mechanism using the beacon frame. While adescription of the components of various blocks is provided inaccordance with the illustrative embodiment, the arrangement may bedifferent depending on the implementation details of a particularconfiguration, whether there is structural or functional overlap betweenthe blocks, or the like.

The MAC block 710 can be provided with a processing unit 711, which canbe a general purpose or special purposes processor provided performanceparameters are met. It will be appreciated that in the case of asoftware implementation, the various detailed algorithms and proceduresas described herein will be transformative to allow any processing unitto specifically implement embodiments of the invention. Alternatively,the processing unit can be specially adapted to carry out operation inaccordance with embodiments based on application specific or customdesign. The processing unit 711 can be accompanied by a memory 712,which can be an on-board or external memory meaning that memory 712 canbe integrated within the same circuit as processing unit 711 or can bean external component or cell, or a combination of both. The componentscan be coupled by a bus connector 713, which can be a serial or parallelbus or connector or some other configuration as will be appreciated.

PHY block 720 can be configured to receive and transmit, for example,signals from and to the radio environment at an in-phase and quadrature(I/Q) block 723 which passes inbound analog signals from the radioenvironment (e.g., a transmission band frequency) to an analog todigital converter (ADC) 724 and passes outbound digital signals (e.g., adigital baseband frequency) to a digital to analog converter DAC 725.The processing unit 711 can also be coupled to external devices orsystems through a connector 714. The MAC block 710 can be coupled to thePHY block 720 through the bus 713, or through similar means, or, may beintegrated with the PHY block 720 subject to signal constraints such asdata rate or the like. It will be appreciated that in some embodiments,the PHY block 720 and MAC block 710 may be integrated, or in embodimentswhere the MAC block 710 is implemented in hardware, the MACfunctionality may be hardware oriented, that is, there is no need tofully decode the probe request packets. Instead, probe requests such asRTT_MEAS_REQ 610, can be recognized at a hardware layer and responded toimmediately, referred to as a hardware MAC layer, in a manner thatreduces processing delays to a negligible amount. It is also possiblethat an acknowledgement can be generated before receipt of the fullrequest is processed as long as enough of the request is processed toidentify it as such. Such an approach reduces processing delay to almostzero.

It will be appreciated that signals may travel to and from the RTT_APPunit 701 in the air interface, and may be sent to and received from theair interface using RF block 730, which can include one or, inaccordance with, for example, antenna diversity arrangements, and thelike, more antenna 732. The RF block can perform down conversion of thetransport frequency signal to an intermediate frequency (IF) signal (notshown), where it can be passed to PHY 720 through an amplifier 721.Generated IF signals can be passed from the PHY block 720 to anamplifier 722 to be passed to the RF block 730 and, if necessary,up-converted for transmission. In some embodiments, direct conversionmay be used, wherein no intermediate frequency conversion of received RFsignals, or signals to be transmitted over the RF block 730, is requiredand signals are converted directly from transport frequency (e.g., atransmission band frequency, such as an 802.11 transmission band) intodigital vectors and processed directly. It will be appreciated that tothe extent that the RF frequency or transport frequency signals can berecognized through either direct conversion or an RF MAC functionality,involving recognition of the signals without conversion, basebanddown-conversion and transport band up conversion can be avoided,acknowledgements can be generated more quickly leading to betterperformance for RTT_APP unit 701 and, thus, greater positional accuracyfor location estimates for STA1 108.

It will be appreciated that in accordance with embodiments, localizationof, for example, a mobile unit such as STA1 108 described herein, can befacilitated through the use of responses generated by dedicatedappliances to requests for measurement related communication such aslocation measurement related communication. In an exemplary method,selected components of which are illustrated in FIG. 8, after start at801, dedicated requests can be optionally sent at 802 that identify arequest as an RTT_MEAS_REQ(APPn), which can be a request type thatindicates a specific request for a measurement related communication,such as an RTT_MEAS_RESP_APPn from a compliant RTT_APPn ((APPn) can bean identifier associated with the appliance RTT_APPn). It should benoted that, while the above example includes reference to a directedrequest to an RTT_APPn, the request can be sent as a unicast, multicastor broadcast communication or combination thereof to one appliance, ifknown, or to many appliances. Alternatively, the request can be sent asa normal probe request in a unicast, multicast or broadcast fashion, inwhich case all access points within range, including RTT_APPs andnon-RTT_APPs alike will respond. The request can be received at 803,such as at an RTT_APP or at any access point within range of the senderof the request. If appropriate, the receiver can recognize or otherwiseidentify the request at 804 as a RTT_MEAS_REQ(APPn), for example, basedon a request type of the request and/or an identifier associated withthe appliance.

A response, such as RTT_MEAS_RESP_APPn, can be immediately generated at805 after uniform processing delay Δ_(RTT) _(—) _(APP). It should benoted that the processing period is referred to herein as a delay evenin a scenario where the actual delay in generating the response is verysmall. Once the request has been fully received, for calculationpurposes there will be some non-zero time amount, however negligible,that represents systematic processing of the response while the receiptof the request is being conducted. The amount however will be uniform orcan be configured to be uniform therefore for calculation purposes canbe factored out as described herein above. In generating the response,it will also be noted that a position of the RTT_APPn using, forexample, (x, y) coordinates can be included in the response to aid inlocalization. In an embodiment, the MAC address of the RTT_APP can belooked up in a database to get the (x,y) coordinates of the RTT_APP.Alternatively, a list of RTT_APPs in a locale can be provided to amobile station when it enters the locale. When a sufficient number ofresponses have been received by the requesting station or, in the casewhere position estimates have already been established, an additionalsingle response has been received, localization can be conducted at 806.Alternatively, refinement of a previous localization procedure orposition estimate can be conducted using one or more responses. Whilethe exemplary method is indicated as being completed at 807, it will beappreciated that the process can be continued indefinitely, for example,as the mobile station is in motion, or the like.

Those of skill in the art will appreciate that in accordance withembodiments described in the present disclosure, information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Further, those of skill in the art will appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

The methods, sequences and algorithms described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processing unit, or in a combination ofthe two. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, a hard disk, a removabledisk, a CD, a DVD, or any other form of storage medium known in the art.An exemplary storage medium is coupled to the processing unit such thatthe processing unit can read information from, and write information to,the storage medium. In the alternative, the storage medium may beintegral to the processing unit.

Accordingly, an embodiment of the invention can include acomputer-readable medium embodying a method for adjusting wireless-basedpositions using relative motion sensors. Accordingly, the invention isnot limited to illustrated examples and any means for performing thefunctionality described herein are included in embodiments of theinvention.

While the foregoing disclosure shows illustrative embodiments of theinvention, it should be noted that various changes and modificationscould be made herein without departing from the scope of the inventionas defined by the appended claims. The functions, steps and actions ofthe claims in accordance with the embodiments of the invention describedherein need not be performed in any particular order. Furthermore,although elements of the invention may be described or claimed in thesingular, the plural is contemplated unless limitation to the singularis explicitly stated.

What is claimed is:
 1. A mobile station, comprising: a transceiver; anda processing unit configured to: determine a first round-trip time (RTT)for a first measurement related communication between the transceiverand a first network device, wherein the first RTT comprises a uniformdelay of time applied during the first measurement related communicationby the first network device; determine a second RTT for a secondmeasurement related communication between the transceiver and a secondnetwork device, wherein the second RTT comprises the uniform delay oftime applied during the second measurement related communication by thesecond network device; and determine, at least in part, a position ofthe mobile station with regard to at least the first and second networkdevices based, at least in part, on the first RTT and the second RTT. 2.The mobile device of claim 1, wherein the processing unit is configuredto determine, at least in part, the position of the mobile station withregard to at least the first and second network devices based, at leastin part, on the first RTT and the second RTT, by: initiatingtransmission, via the transceiver, of the first RTT and the second RTTto another device; and in response, receiving from the another device,via the transceiver, the position of the mobile device.
 3. The mobiledevice of claim 1, wherein the processing unit is further configured to:determine a received signal strength measurement for at least one signalreceived via the transceiver from at least transmitting device; anddetermine, at least in part, the position of the mobile station furtherbased, at least in part, on the received signal strength.
 4. The mobilestation of claim 1, wherein at least one of the first network device orthe second network device is part of a short-range wireless network. 5.The mobile station of claim 1, wherein the transceiver supports an802.11 transmission band.
 6. An apparatus for use in a mobile station,the apparatus comprising: means for determining a first round-trip time(RTT) for a first measurement related communication between thetransceiver and a first network device, wherein the first RTT comprisesa uniform delay of time applied during the first measurement relatedcommunication by the first network device; means for determining asecond RTT for a second measurement related communication between thetransceiver and a second network device, wherein the second RTTcomprises the uniform delay of time applied during the secondmeasurement related communication by the second network device; andmeans for determining, at least in part, a position of the mobilestation with regard to at least the first and second network devicesbased, at least in part, on the first RTT and the second RTT.
 7. Theapparatus of claim 6, wherein the means for determining, at least inpart, the position of the mobile station further comprise: means forsending the first RTT and the second RTT to another device; and meansfor receiving, in response from the another device, the position of themobile device.
 8. The apparatus of claim 6, and further comprising:means for determining a received signal strength measurement for atleast one signal received via the transceiver from at least transmittingdevice; and means for determining, at least in part, the position of themobile station further based, at least in part, on the received signalstrength.
 9. The apparatus of claim 6, wherein at least one of the firstnetwork device or the second network device is part of a short-rangewireless network.
 10. A method for use in a mobile station, the methodcomprising, at the mobile station: determining a first round-trip time(RTT) for a first measurement related communication between thetransceiver and a first network device, wherein the first RTT comprisesa uniform delay of time applied during the first measurement relatedcommunication by the first network device; determining a second RTT fora second measurement related communication between the transceiver and asecond network device, wherein the second RTT comprises the uniformdelay of time applied during the second measurement relatedcommunication by the second network device; and determining, at least inpart, a position of the mobile station with regard to at least the firstand second network devices based, at least in part, on the first RTT andthe second RTT.
 11. The method of claim 10, and further comprising, atthe mobile station: sending the first RTT and the second RTT to anotherdevice; and receiving, in response from the another device, the positionof the mobile device.
 12. The method of claim 10, and furthercomprising, at the mobile station: determining a received signalstrength measurement for at least one signal received via thetransceiver from at least transmitting device; and determining, at leastin part, the position of the mobile station further based, at least inpart, on the received signal strength.
 13. The method of claim 10,wherein at least one of the first network device or the second networkdevice is part of a short-range wireless network.
 14. A non-transitionalcomputer-readable medium having instructions stored therein that areexecutable by a processing unit of a mobile station to: determine afirst round-trip time (RTT) for a first measurement relatedcommunication between the transceiver and a first network device,wherein the first RTT comprises a uniform delay of time applied duringthe first measurement related communication by the first network device;determine a second RTT for a second measurement related communicationbetween the transceiver and a second network device, wherein the secondRTT comprises the uniform delay of time applied during the secondmeasurement related communication by the second network device; anddetermine, at least in part, a position of the mobile station withregard to at least the first and second network devices based, at leastin part, on the first RTT and the second RTT.
 15. The non-transitionalcomputer-readable medium of claim 14, wherein the instructions arefurther executable by the processing unit of the mobile station to: sendthe first RTT and the second RTT to another device; and receive, inresponse from the another device, the position of the mobile device. 16.The non-transitional computer-readable medium of claim 14, wherein theinstructions are further executable by the processing unit of the mobilestation to: determine a received signal strength measurement for atleast one signal received via the transceiver from at least transmittingdevice; and determine, at least in part, the position of the mobilestation further based, at least in part, on the received signalstrength.
 17. The non-transitional computer-readable medium of claim 14,wherein at least one of the first network device or the second networkdevice is part of a short-range wireless network.